Borrowed Funds - Short-Term Credit Lines Available for Use (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
FRB's Discount Window Primary Credit Program
Line of Credit Facility [Line Items]
Amount outstanding	$ 874,256	$ 881,113
Available federal funds lines
Line of Credit Facility [Line Items]
Amount outstanding	718,000	684,000
Correspondent bank line of credit
Line of Credit Facility [Line Items]
Amount outstanding	$ 50,000	$ 50,000